1. Field of the Invention
The present invention relates to a thin film magnetic head and a manufacturing method for the same and, more particularly, to a thin film magnetic head having a very narrow track width of 1 xcexcm or less, and a manufacturing method for the same.
2. Description of the Related Art
FIG. 26 shows a conventional flying magnetic head 150.
The flying magnetic head 150 is primarily constructed by a slider 151 and a composite thin film magnetic head 157 provided on the slider 151. Reference numeral 155 denotes a reading end of the slider 151 that is an upstream end of a direction in which a magnetic recording medium moves, while reference numeral 156 denotes a trailing end. Rails 151a, 151a, and 151b are formed on a medium opposing surface 152 of the slider 151, air grooves 151c and 151c being provided between the rails.
The composite thin film magnetic head 157 is provided on an end surface 151d at the trailing end 156 of the slider 151.
Referring to FIGS. 27 and 28, the composite thin film magnetic head 157 is comprised of an MR magnetic head h1 equipped with a magnetoresistive device and a thin film magnetic head h2, which is a write head. These magnetic heads h1 and h2 are deposited on the end surface 151d of the slider 151.
The MR magnetic head h1 is comprised of a lower shield layer 163 that is formed on the end surface 151d of the slider 151 and composed of a magnetic alloy, a read gap layer 164 deposited on the lower shield layer 163, a magnetoresistive device 165 exposed on the medium opposing surface 152, an upper shield planarizing gap layer 166 covering the magnetoresistive device 165 and the read gap layer 164, and an upper shield layer 167 covering the upper shield planarizing gap layer 166.
The upper shield layer 167 serves also as a lower core layer of the thin film magnetic head h2.
The MR magnetic head h1 is employed as a read magnetic head. When a minute leakage magnetic field from a magnetic recording medium is applied to the magnetoresistive device 165, resistance in the magnetoresistive device 165 changes. A voltage change based on the change in the resistance is read as a reproduction signal of the magnetic recording medium by the MR magnetic head h1.
The thin film magnetic head h2 is formed of a lower core layer or the upper shield layer 167, a gap layer 174 deposited on the lower core layer 167, a coil 176 formed in a back region Y of the gap layer 174, an upper insulation layer 177 covering the coil 176, and an upper core layer 178 that is joined to the gap layer 174 in a magnetic pole tip region X and joined to the lower core layer 167 in the back region Y.
The coil 176 is patterned so that it is flatly spiral. In a substantially central portion of the coil 176, a proximal end portion 178b of the upper core layer 178 is magnetically connected to the lower core layer 167.
A protective layer 179 composed of alumina or the like is deposited on the upper core layer 178.
The lower core layer 167, the gap layer 174, and the upper core layer 178 extend from the back region Y toward the magnetic pole tip region X in the composite thin film magnetic head 157, and are exposed on the medium opposing surface 152. In the medium opposing surface 152, the upper core layer 178 and the lower core layer 167 face each other with the gap layer 174 sandwiched therebetween, forming a magnetic gap.
The magnetic pole tip region X is an area where the upper core layer 178 and the lower core layer 167 are separated by only the gap layer 174 sandwiched therebetween in the vicinity of the medium opposing surface 152. The back region Y refers to an area excluding the magnetic pole tip region X.
The foregoing thin film magnetic head h2 is used as a write head. When a recording current is applied to the coil 176, magnetic fluxes are generated in the upper core layer 178 and the lower core layer 167 by the recording current. The magnetic fluxes leak out through the magnetic gap to produce a leakage magnetic field, and the leakage magnetic field causes the magnetic recording medium to be magnetized to thereby record a recording signal.
To fabricate the thin film magnetic head h2, the lower core layer 167, the gap layer 174, and the upper core layer 178 are formed in this order by a depositing pattern in advance. In this case, the upper core layer 178 is processed according to a frame plating method using plating and ion milling. A width of the upper core layer 178 exposed to the medium opposing surface 152 is determined by a resist width in the frame plating method or the like, the plating, and an etching method, and the width of the upper core layer 178 exposed on the medium opposing surface 152 determines a magnetic recording track width.
Thus, a track width of a magnetic recording medium can be reduced by providing a smaller magnetic recording track width of the thin film magnetic head h2, i.e., the width of the upper core layer 178 at the magnetic pole tip exposed on the medium opposing surface. This makes it possible to achieve a higher track density of the magnetic recording medium, consequently permitting a higher recording density.
In the conventional thin film magnetic head h2, however, the upper core layer is thick. Therefore, even when the layers are accurately formed by the frame plating or other means and the magnetic pole tip is processed with the highest possible processing accuracy currently available, it is difficult to accomplish a recording track width of 1 xcexcm or less due to a limited resolution of exposure when forming a resist pattern. This has been a problem in that a further higher recording density of a magnetic recording medium cannot be achieved.
Accordingly, the present invention has been made with a view toward solving the problem described above, and it is an object thereof to provide a thin film magnetic head having a recording track width of 1 xcexcm or less. It is another object thereof to provide a method for manufacturing a thin film magnetic head having a recording track width of 1 xcexcm or less.
To fulfill the foregoing objects, the present invention adopts the following configurations.
According to one aspect of the present invention, there is provided a thin film magnetic head including: an upper core layer and a lower core layer that extend from a back region toward a magnetic pole tip region, end surfaces thereof being exposed on a medium opposing surface, and the upper core layer and the lower core layer being magnetically connected in the back region; and a gap layer provided between the upper core layer and the lower core layer in the magnetic pole tip region; wherein an insulation layer is deposited on the lower core layer; a groove extending from the medium opposing surface toward the back region is provided in the magnetic pole tip region of the insulation layer, the groove being composed of a groove main body that opens to the lower core layer, the upper core layer, and the medium opposing surface, and a slant portion formed in the opening of the groove main body at the end of the upper core layer; a lower magnetic pole layer, the gap layer, and an upper magnetic pole layer are deposited in the groove; and the lower magnetic pole layer is joined to the lower core layer, while the upper magnetic pole layer is joined to the upper core layer, the upper magnetic pole layer forming an upper magnetic pole tip, while the lower magnetic pole layer forms a lower magnetic pole tip.
In a preferred form of the present invention, the groove main body of the thin film magnetic head is equipped with two side walls that are installed in a standing manner on the lower core layer and reach the medium opposing surface, and a magnetic pole tip surface that connects the two side walls at the back region side of the groove main body and defines gap depths of the upper magnetic pole tip and the lower magnetic pole tip.
In another preferred form of the present invention, the slant portion is composed of two slant surfaces near the side walls and a magnetic pole tip slant surface that continues to the magnetic pole tip surface.
In a further preferred form of the present invention, the lower magnetic pole layer and the gap layer are deposited in the groove main body, and the upper magnetic pole layer is deposited such that it extends over the groove main body and the slant portion.
In a further preferred form of the present invention, a top surface of the lower core layer is polished.
In the thin film magnetic head according to the present invention, the lower core layer and the lower magnetic pole layer make up a lower core, while the upper core layer and the upper magnetic pole layer make up an upper core. Furthermore, the lower magnetic pole layer, the gap layer, and the upper magnetic pole layer make up a magnetic gap, and the magnetic gap lies between the upper core and the lower core.
A part of the lower magnetic pole layer, the gap layer, and the upper magnetic pole layer that constitute the magnetic gap is deposited in the groove main body formed beforehand, so that a recording track width is decided by a width of the groove main body. Hence, the recording track width can be reduced by reducing the width of the groove main body.
Moreover, in the thin film magnetic head according to the present invention, the gap depth of the magnetic gap is defined by a distance from the medium opposing surface to a magnetic pole tip surface of the groove main body, and a part of the lower magnetic pole layer, the gap layer, and the upper magnetic pole layer that constitute the magnetic gap is deposited in the groove main body, thus eliminating a possibility of variations in the gap depth.
The upper magnetic pole layer is deposited over the groove main body and the slant portion and joined to the upper core layer, so that a tapered portion is formed on the upper magnetic pole layer at the upper core layer side. The presence of the tapered portion ensures smooth flow of magnetic fluxes between the upper core layer and the upper magnetic pole layer, preventing the magnetic fluxes from leaking at a junction between the upper core layer and the upper magnetic pole layer.
The top surface of the lower core layer is polished to be a flat surface having a surface roughness of 0.001 xcexcm to 0.015 xcexcm. This enables the groove to be formed with high accuracy, thereby allowing the recording track width to be reduced.
It is also possible to reduce the gap between the side walls of the groove main body to 1 xcexcm or less, and more preferably to 0.5 xcexcm or less. Thus, the recording track width can be set to 1 xcexcm or less.
Preferably, slope angles of the slant surfaces near the side walls range from 10 to 80 degrees with respect to the lower core layer in the thin film magnetic head in accordance with the present invention.
Preferably, a slope angle of the magnetic pole tip slant surface ranges from 10 to 80 degrees with respect to the lower core layer.
If the slope angles of the slant surfaces near the side walls are below 10 degrees, then a reactance between the upper core layer and the lower core layer will be undesirably reduced with a consequent increased leakage magnetic flux at an end of the magnetic recording track. Conversely, if the slope angles exceed 80 degrees, then the volume of the upper magnetic pole layer is reduced and a reactance of the upper magnetic pole layer is increased. This will undesirably lead to a loss in magnetic fluxes supplied from the upper core layer to the upper magnetic pole layer with a consequent reduction in an amount of effective magnetic fluxes in the magnetic gap.
Likewise, if the slope angle of the magnetic pole tip slant surface is below 10 degrees, then the reactance between the upper core layer and the lower core layer will be undesirably reduced with a consequent increase in a leakage magnetic field from the upper core layer to the upper magnetic pole layer in the vicinity of the magnetic pole tip slant surface. Conversely, if the slope angle of the magnetic pole tip slant surface exceeds 80 degrees, then a sectional configuration of the upper core layer cannot be smoothly formed, and a part of the sectional configuration of the upper core layer will have an acute angle. As a result, a large diamagnetic field undesirably increases in the vicinity of the acute angle, thus leading to lower recording efficiency.
Preferably, in the thin film magnetic head according to the present invention, the insulation layer, the lower magnetic pole layer, the gap layer, and the upper magnetic pole layer are exposed on the medium opposing surface. With this arrangement, the recording track width on the medium opposing surface coincides with the width of the groove main body of the insulation layer, so that the recording track width can be reduced. In addition, since the magnetic gap is exposed through the medium opposing surface, the leakage magnetic field produced from the magnetic gap permits efficient magnetic recording on a magnetic recording medium.
Preferably, the insulation layer is formed of a single-layer film composed of one of AlO, Al2O3, SiO, SiO2, Ta2O5, TiO, AlN, AlSiN, TiN, SiN, Si3N4, NiO, WO, WO3, BN, and CrN, or a multi-layer film wherein two or more different single-layer films are laminated. Forming the insulation layer by using the components mentioned above permits anisotropic etching to be carried out for forming the groove. This eliminates a possibility of side etching, thus enabling higher dimensional accuracy of the width of the groove, namely, the groove main body, especially in a direction of the depth of the groove.
Preferably, the gap layer is formed of a single-layer film composed of one of Au, Pt, Rh, Pd, Ru, Cr, a NiMo alloy, a NiW alloy, a NiP alloy, and NiPd alloy, or a multi-layer film wherein two or more different single-layer films are laminated.
All the above constituents are nonmagnetic and are not magnetized, making themselves ideally suited for constituting a gap layer of a thin film magnetic head. These constituents are metallic and can be deposited in a groove by an electroplating method using an underlying core layer as an electrode. Hence, the gap layer can be securely formed in the main body of the groove, enabling the width of the gap layer to agree with the width of the groove main body.
Preferably, the upper magnetic pole layer and the lower magnetic pole layer are formed of a single-layer film composed of one of a FeNi alloy, a FeNi alloy in which the concentration of Fe is higher than that of Ni, and a CoFeNi alloy, or a multi-layer film wherein two or more different single-layer films are laminated.
The above constituents are all magnetic constituents featuring superior soft magnetic characteristics and ideally suited for constituting a core of a thin film magnetic head. In addition, these constituents are metallic and can be deposited in the groove by the electroplating method using an underlying core layer as an electrode.
Furthermore, the composite thin film magnetic head in accordance with the present invention is composed of a read magnetic head equipped with a magnetoresistive device and the thin film magnetic head described above, these two magnetic heads being laminated.
According to another aspect of the present invention, there is provided a manufacturing method for a thin film magnetic head having an upper core layer and a lower core layer that extend from a back region toward a magnetic pole tip region to be exposed on a medium opposing surface, the upper core layer and the lower core layer being magnetically connected in the back region, and a gap layer provided between the upper core layer and the lower core layer in the magnetic pole tip region, the method including the steps of: polishing a top surface of the lower core layer to planarize it, and depositing an insulation layer on the lower core layer; forming, in the magnetic pole tip region of the insulation layer, a groove that extends from the medium opposing surface toward the back region, and making a bottom surface of the groove reach the lower core layer; depositing the lower magnetic pole layer, the gap layer, and the upper magnetic pole layer in the groove, and joining the lower core layer and the lower magnetic pole layer; forming a coil in the back region of the insulation layer, and joining the coil to the upper magnetic pole layer in the magnetic pole tip region; and forming the upper core layer that covers a part of the coil in the back region.
Preferably, the insulation layer is subjected to anisotropic etching to form the groove.
Polishing the lower core layer to planarize it leads to a flat insulation layer to be deposited in a subsequent step. This makes it possible to accurately form the groove by the anisotropic etching, permitting the recording track width to be reduced.
Forming the groove by the anisotropic etching prevents side etching, enabling improvement of the dimensional accuracy of the groove width in relation to the direction of the groove depth.
Preferably, when forming the groove, a mask layer is deposited on the insulation layer, a pattern is formed on the mask layer, and the anisotropic etching is performed on the insulation layer exposed through the pattern.
The anisotropic etching is most preferably performed by a reactive ion etching method. This allows the groove to be formed with high dimensional accuracy.
Preferably, the mask layer is one of a photoresist layer, a metal film layer, a laminate composed of a photoresist layer and a metal film layer, and a metal oxide layer.
The photoresist layer may be a standard positive or negative photoresist, or a photoresist that can be exposed by far ultraviolet rays, electron beams, X-rays, ion beams, or the like.
The metal film layer is preferably composed of one or more of Ti, Zr, Nb, Ta, Cr, Mo, W, Ru, Co, Rh, Ir, Ni, Pd, Pt, Au, Al, In, and Si, and may be formed of a single-layer film or a multi-layer film composed of the single-layer films.
The metal oxide layer is preferably composed of one or more of SiO, SiO2, TaO, Ta2O5, TiO, SiN, Si3N4, CrO, WO, ZrO, NiO, AlO, and IrO, and may be formed of a single-layer film or a multi-layer film composed of the single-layer films.
A reactant gas used for forming the groove by the reactive ion etching method is preferably composed of one or more of CF4, a mixed gas of CF4 and O2, C2F6, a mixed gas of C2F6 and O2, C4F6, a mixed gas of C4F6 and O2, Cl2 BCl3, a mixed gas of Cl2 and BCl3, CHF3, and a mixed gas of CHF3 and Ar. Among these reactant gases, a best suited one is selected based on constituents of the insulation layer and the mask layer.
In the manufacturing method for a thin film magnetic head in accordance with the present invention, it is preferable to apply an ion beam to a portion where the top surface of the insulation layer and the groove are connected, to perform etching after forming the groove thereby to form a groove main body that opens to the lower core layer, the upper core layer, and the medium opposing surface and to form a slant portion in an opening of the groove main body at the end of the upper core layer.
Preferably, the slant portion on the insulation layer is formed by performing reactive etching under a condition for taper-edging a resist.
Preferably, the lower magnetic pole layer and the gap layer are deposited on the groove main body, and the upper magnetic pole layer is deposited over the groove main body and the slant portion.
Preferably, the lower magnetic pole layer, the gap layer, and the upper magnetic pole layer are formed by the electroplating method using the lower core layer as an electrode.
In the manufacturing method for a thin film magnetic head according to the present invention, a coil insulation layer having a slant surface that inclines toward the magnetic pole tip slant surface is formed between the insulation layer and the coil.